This invention relates generally to automatic door systems which employ approach and safety sensor systems to provide input for controlling the position of a door. More particularly, the present invention relates to automatic swing doors which employ mats to provide input signals to open and close the door or maintain the position of the door.
In automatic door systems to which the invention relates, a swing door operator swings a door from a closed to a full open position and maintains the position and/or closes the door in response to signals from an electronic controller. Typically, an approach mat or an approach sensor provides a signal to the control system to open or maintain the door in an open position. A safety mat is positioned on the egress side of the swing door to maintain the door in an open position as a person passes through the doorway and also to prevent a door from swinging open into the path of a person who may be standing at the swing side of a closed door. In conventional fashion, the control system receives input signals from the approach mat or approach sensor and the safety mat and processes the signals to provide the opening, closing and positioning logic for the proper operation of the door. The control transmits commands to the operator to implement various time delays and to control the speed, direction and power limiting functions for the door.
In conventional systems for which the invention has applicability, when a person steps on an approach mat, the door swings to a full open position and remains fully open while the person is on the approach mat. If the person steps off the approach mat without crossing the threshold, a timer starts. After expiration of a pre-established time interval, such as, for example, six seconds, the door will begin a closing cycle. Commonly, the closing speed is reduced as the swing door approaches the closed position. The control logic generates a hold open delay signal when a person steps on the approach mat and crosses the threshold of the open door. As long as the person stays on the safety mat, the door remains in the open position. If the person leaves the safety mat, the door typically closes after a pre-established second hold open delay which is typically one and a half seconds. As an additional safety feature, if a person is standing on the safety mat and a person steps on the approach mat or comes within the approach sensor, the door will not open but will remain in the closed position. Once the person steps off the safety mat, the door will resume a normal cyclical operation upon expiration of a safety delay time interval.
Proper functioning of the approach and safety mats is a predicate to proper operation of the automatic door system. It is highly desirable that the operational sequence be routinely checked and that the mats be thoroughly checked to verify that they provide good contact characteristics throughout the effective contact area of the mats. Under normal conditions, thorough monitoring of the mats or the approach sensor cannot be accomplished in an efficient time effective manner because the door would normally recycle through the various operational sequences. Consequently, in practice, thorough monitoring of the approach and safety mats may be compromised by the time required to carry out the monitoring task.